Changes in peptide composition of lactic acid bacteria fermented chickpea flour and its functional implications

The potential for plant-based ingredients to replace animal proteins in the Western diet remains unrealised due to the presence of flavour notes that are often described as bitter or grassy and tend to decrease consumer liking. Fermentation has been identified as a promising intervention that could tackle challenges associated with legumes through the enzymatic cleaving of plant-based proteins into smaller molecules and peptides that could potentially improve function and sensorial properties. Flour (21% w/w protein, 6% w/w fat) prepared from a desi chickpea variety commonly cultivated in Australia was fermented with lactic acid bacteria (three different Leuconostoc mesenteroides strains). The proteolytic activity and cleavage frequencies of each stain was assessed by comparing peptidomic profiles to an unfermented control.  The solubility, GRAVY index and bitterness predictions were calculated to understand the implications of these molecular changes in protein to sensorial properties and function. 

The peptidomics analysis identified 99 fermentation-derived peptides. Cleavage site analysis revealed a preference for hydrophobic residues, such as leucine, phenylalanine, and valine, which have been linked previously by others to the generation of desirable volatile compounds during enzymatic reactions or thermal processing. Forty-one of the 99 peptides are predicted to contribute to bitterness. GRAVY index analysis indicated that 42% of peptides were highly hydrophilic (GRAVY index < -0.5), 6% were hydrophobic (GRAVY index > 0.5), and the remaining (51%) displayed intermediate hydrophobicity. Moreover, fermentation irreversibly decrease solubility (at pH 7). Consumer testing is required to confirm if these molecular changes are beneficial, depending on the end use and further processing steps. These findings provide a foundation for future research aimed at optimizing Leuconostoc mesenteroides-mediated fermentation processes to enhance the functional and sensory attributes of chickpea-based products.